The Phoenix Mars Lander is on its way to Mars after a spectacular pre-dawn launch Saturday at Cape Canaveral, Florida. The probe will search for signs that life could ever have existed in the northern polar region of the planet. As we hear from Mike O'Sullivan, the craft also carries a digital library that shows our human fascination with Mars.

After a nine-month journey, the probe will search beneath the frozen Martian surface for hints of an environment compatible with life, such as water and organic chemicals.

Bruce Betts of the nonprofit Planetary Society says the organization has prepared a gift for future visitors to Mars, a silica-glass DVD attached to the deck of the lander.

"And that DVD has two things on it. One, it's got a quarter-million names of people who signed up to send their names to Mars, participate that way in the mission. And then it's got the first library for Mars, which we call Visions of Mars, that has all sorts of stories and art about the Red Planet," he said.

There are works of fiction and works of science by writers such as Isaac Asimov, Ray Bradbury, Arthur C. Clarke and astronomer Carl Sagan. Sagan was one of the founders of the Planetary Society.

Betts says the distinctive red planet has always stirred the imagination. The 19th century observer Percival Lowell thought he saw canals there. It was an illusion, but the erroneous observation led to wild speculation about a Martian civilization. Lowell's work is part of the digital library.

The disk also includes a work of fiction by H.G. Wells called The War of the Worlds. The DVD has the original text version of the story and its radio adaptation in a realistic 1938 broadcast.

The dramatization of an invasion by Martians was so convincing that it sparked a panic in some parts of the United States.

Betts says Phoenix is just one of a number of missions to Mars that are under way or planned by the U.S. space agency NASA and the space agencies of Europe and Russia. He notes there are launch opportunities every 26 months, when the Earth, Mars and Sun are properly aligned, and he sees a busy schedule ahead in coming launch windows.

"In the next opportunity in 2009, NASA will send a really big rover called Mars Science Laboratory, and it will actually have some of the first experiments since Viking in the 1970s that really look more directly for life as opposed to just studying questions of: could there have been life? Was there habitability," he said.

Russia is planning a 2009 sample return mission to the Martian moon Phobos. Two years later, a U.S. mission will study the upper atmosphere of Mars, and 2013 should see the launch of a NASA orbiter and a European rover.

Beyond that, the United States plans to return humans to our own moon by 2020, and then use the moon as a base for a human journey to Mars.